1. Field of the Invention
The present invention relates to a measurement method and apparatus for quantifying physical or chemical phenomena and, for example, to a measurement method and apparatus for quantifying various physical or chemical phenomena such as the two-dimensional distribution of solution pH, pressure, magnetic field, or temperature.
2. Description of the Related Art
Physical or chemical phenomena include various phenomena such as concentration, temperature, magnetism, pressure, acceleration, speed, sound wave, supersonic wave, oxidation-reduction potential, and reaction rate, and these phenomena can be converted into various electric signals (electric current, voltage, resistance, electric charge capacity, and potential).
There is a method of measuring physical or chemical phenomena by converting them into electric charge information, such as a method of measuring the amount of light by converting the amount of light into the amount of electric charge and evaluating the amount of electric charge, by using a device such as a photodiode which upon irradiation with light forms a pair of electron holes corresponding to the amount of the light.
For measurement of physical and chemical phenomena other than light, however, the phenomena are converted in almost all cases not into the amount of electric charge but into electric signals such as voltage value, electric current value or resistance value, and these values are read, so accumulation and transmission, that is, processing methods unique to electric charge, is infeasible, and high-speed processing by simultaneous incorporation of information in a plurality of points, or conversion of measurement results into an image, is very difficult.
In various fields including environmental or medical fields, demand for such high-speed processing or conversion of physical or chemical phenomena into an image is increasing in recent years, and for example, there is proposed a method and apparatus for converting various physical or chemical phenomena easily into images, wherein a potential well constituted so as to have depth changed depending on the magnitude of physical or chemical amount is supplied with electric charge, and the physical or chemical amount is converted into electric charge depending on the magnitude of the potential well, whereby information in a plurality of points is simultaneously incorporated, followed by accumulation, transmission etc. (see, for example, JP-A 10-332423).
In measurement of physical or chemical phenomena at present, however, there is need for higher measurement accuracy and rapider response than before, and there is increasing demand for improvements in accuracy and response in the method and apparatus described above.
That is, when physical or chemical phenomena are converted into electric charge information, it is an urgent task to decide which constitution and structure are preferable for accuracy or response as the means of transferring electric charges in order to transfer electric charges efficiently and rapidly.
In measurement of physical or chemical phenomena, there are the case where a large amount of electric charges are transferred by a large change in phenomena and the case where a very small amount of electric charges are transferred due to a very small change in physical or chemical phenomena. In both the cases in actual measurement, a predetermined measurement accuracy corresponding to the change in phenomena is required, but under the transfer conditions of electric charges in both the cases, the same accuracy is hardly secured with detectors having the same constitution. That is, it is an urgent task for the detector to secure linearity in a broad range.